This is an application for an Autoradiographic Digital Imager (ADI). The ADI is an innovative, real-time imager, utilizing state-of-the-art image tube and solid-state detector array and microcircuit technology, to acquire biopsy radiopharmaceutical spatial distributions. ADI resolution is expected to be less than 10um, approaching that of film, but will be much more convenient to use than film. The dynamic range of the instrument is effectively infinite and it is linear over the full dynamic range. The ADI is high-speed and, therefore, detects individual disintegrations with high sensitivity. Because of its high speed and energy resolution capability, it can distinguish more than one radiopharmaceutical in a single tissue specimen. The ADI will be exceedingly useful for radioimmunotherapy where a detailed knowledge of dose variation at the cellular level is necessary to obtain a rationale for therapy optimization. The technical objective of the Phase I effort is the detailed design and computer simulation, performance verification of the ADI. A researcher in the field of microdosimetry and radioimmunotherapy will support the practical application aspects of the design, as a consultant. The output of the Phase I program will be the design parameters that will be used in Phase II to fabricate the device. The technical objective of Phase II is the fabrication and testing of an ADI prototype.